I. Field of the Invention
The invention relates to a tube-bundle heat exchanger, especially intended for cooling supercharging air in a supercharged internal combustion engine of a motor vehicle.
The invention relates more particularly to a heat exchanger, especially of the air-to-air type, for a supercharged internal combustion engine, of the type provided with at least one first manifold and one second manifold, which are connected transversely by a bundle of horizontal tubes, in which there circulates an internal air flow to be cooled by a flow of cooling fluid circulating outside the tube bundle.
II. Description of Related Art
In supercharged internal combustion engines, it is known that cooling devices or “intercoolers”, such as a thermal or heat exchanger, can be used to cool the supercharging air in order to reduce the heat load on the engine, the temperature of the exhaust gases and consequently the NOx emissions and the fuel consumption.
The supercharging air can be cooled primarily in two ways, either by the cooling fluid of the engine or by the outside ambient air.
In the case of cooling by water, the position at which the intercooler is mounted—typically an exchanger of the air-to-water type—can be chosen freely, which is highly advantageous in view of the extreme compactness of water-cooled intercoolers. Nevertheless, it is not possible to lower the temperature of the supercharging air to the desired value, which is generally below that of the cooling fluid.
This is the reason for which motor vehicles provided with supercharged or turbocompressed internal combustion engines are almost exclusively equipped with air-cooled intercoolers for the supercharging air, generally in the form of at least one heat exchanger of the air-to-air type.
U.S. Pat. No. 4,702,079 describes an example of a heat exchanger of the air-to-air type which, as can be seen in particular from FIG. 2 of that document, is most often mounted at the front of the vehicle in such a way that it is ventilated by the dynamic pressure of the outside air when the vehicle is in motion.
Of course, the air-to-air exchanger can also be placed in a different location of the engine compartment of the vehicle, but then it must be ventilated by means of a separate blower, such as a motorized fan assembly. Because of costs, weight and space requirements, therefore, such a solution is rarely employed.
In the case of installation of the exchanger at the front of the vehicle, it is also necessary to take other constraints into consideration, more particularly constraints relating to safety, such as respect for standards relating to a collision with a pedestrian.
Thus the air-to-air exchanger is generally placed in front of the water radiator, with the advantage of always having sufficient cooling at low speed by virtue of the presence of the fan of the water radiator.
On the other hand, however, such an installation runs the risk of obstructing the circulation and arrival of outside cooling air and the drawback of “preheating” the cooling air, with the consequence that the water radiator has to be overdimensioned.
In order to remedy these disadvantages, solutions are being sought that permit the exchangers (or intercoolers) for the supercharging air to be installed above or below the water radiator.
Nevertheless, such an installation necessitates using, especially for reasons of space requirement, a heat exchanger having appropriate length, width and height dimensions, meaning an exchanger in the overall shape of a “bar”, wherein the tube bundle has great length compared with its respective width and height.
In a heat exchanger, the head loss for a given number of tubes increases with the length of the bundle tubes through which the supercharging air flow is passing.
In addition, the bundle tubes are generally provided with means such as “turbulators”, so named because they bring about turbulent or non-laminar flow of the air to be cooled, for the purpose of increasing the heat exchanges between the air to be cooled and the cooling fluid.
Therefore, the scope of head losses in such exchangers heretofore has compromised their use in applications for cooling the supercharging air of an internal combustion engine.